The present invention relates to a composite sheet material mainly consisting of a wood cellulosic filler and an olefinic plastic and, in particular, relates to the composite sheet material bonded with a wooden part or member of an article or a surface material of a non-woven fabric of a polyester fiber, a paper, a pulp or the like.
A composite sheet material is broadly used for components of an automobile and mainly consists of an olefinic plastic such as polyethylene, polypropylene and the like and a wood cellulosic filler produced by crushing or pulverizing a wood or lumber, a hardboard, a pulp or the like into a predetermined size.
Such a component is made by usually laminating or integrating simultaneously together with a surface material of a non-woven fabric of a polyester fiber, a paper, a pulp or the like in an extrusion molding process of the composite sheet material.
As one technique, the composite sheet material is molded and is then heated. Then, the surface material described above is put thereon and those materials are pressed together in a mold, so that a component having a layered structure can be made. In this technique, a polyolefinic plastic film as a hot melt film must be put between those materials so as to form a sandwich structure to press and mold those materials together with the film. Otherwise, the desired bond strength (for example, the hot water resisting property) between those materials cannot be achieved. Note that the hot water resisting test is done by observing whether a relief is appeared at an end side of a bond portion or not after heating and drying it at 60xc2x0 C. for 2 hours after dipping it into hot water at 70xc2x0 C. for 3 hours. If the relief is not appeared, the hot water resisting property is said to be good.
In another technique, the composite sheet material described above can be adhered to the surface material or the wooden part or member by use of an adhesive. In this technique, a surface of the composite sheet material is, in advance, sanded or rubbed with a sand paper. Note that this sanding process may be carried out after the hot molding process of the composite sheet material is completed or may be carried out on the composite sheet material which has not undergone such a hot molding process.
In this technique, as well as the above technique, the desired bond strength such as the hot water resisting property can not be achieved because of influence of the inactive olefinic plastic mixed in the composite sheet material.
In order to improve the adhesive property of the composite sheet material, the surface thereof is sanded as described above. In such a technique, the amount of the wood cellulosic filler used is increased to 50%-60% to improve the adhesive property. That is, this composite sheet material contains too much amount of the wood cellulosic filler. This induces that the frictional heating produced during the sanding process softens polypropylene, and in addition to this matter, the sand paper is blinded by microscopic chips or waste produced during the sanding process. Such chips or waste are difficult to remove by means of air blowing, and as a result, the efficiency of the sanding process is considerably reduced and the sand paper must be frequently changed.
Therefore, the present invention is made to solve those problems, and an object of the present invention is to provide a bondable wood cellulosic filler/olefinic plastic composite sheet material which can be welded to a variety of surface materials and has a good bond strength without using any welding materials.
Another object of the present invention is to provide a bondable wood cellulosic filler/olefinic plastic composite sheet material which can be welded to a variety of surface materials and has a good bond strength without requiring any means of pliers and carrying out any further surface treatments.
Still another object of the present invention is to provide a bondable wood cellulosic filler/olefinic plastic composite sheet material in which a sand paper used for sanding the composite sheet material is not easily blinded and microscopic chips or waste, which are produced during the sanding process, attached to the sand paper can be easily removed by means of air blowing.